I have played a pawn two squares (avoiding capture by moving one square) about 5 or 6 times recently, and not once has my opponent captured my pawn "En Passant". In some of these situations, it would have been quite advantageous to do so. Could it be that many online players are unaware or confused by this rule?

Yes, many beginner players just starting out with the game of chess do not know of the En Passant move.

 

To read more about the "en passant" rule please visit:
http://www.chess.com/chessopedia/view/en-passant

I guess it could also have a little to do with being away from a game, and coming back to it the next day. It is something that could be overlooked.

Yep, En passant can be deadly. The first time I played it my opponent looked at me like I had no idea what I was doing and had the tournment come over to check. Pretty funny, but not for him. It's not a very common topic I guess

I know about enpassant.  Years ago I didn't understand it.  Now I do.  I really don't think about it much.  Of all the games I have played on www.chess.com I have never used it against my opponent because it never came up.  However one game my opponent used it against me because it is one of the moves I do not think about much.  It turned the game around and I lost the game.

Never seem to use it. I understand it perfectly, however.

enpasante is an additional move added to the rules of chess. before when people moved their pawns 2 spaces to avoid being captured; it frustrated many oponenets and led to many draw games becasue of that. i really like the move and have come across it couple of times. "en passaunte," means "in passing" by the way and it should be considered seriously-for it is a very good weapon.

I rarely use it.  I think that in most cases, intermediate players won't give the right circumstances - you have to focus your movement on one pawn, possibly three, instead of most of your pieces.  Trying to do that, a good opponent can outmaneuver you and put you in a very bad position.  That's usually what happens when I use it against my opponent.  Also, if your opponent knows about en passant, they won't give you the chance to use it. 

I have used en passant a couple of times in my games here, and the last time just baffled my opponent. I've landed some serious blows with it and I'm glad that the move was invented.

Some folks may not know it.  They may not know about underpromotion or the 50 move rule.  But ultimately it lies on one's own shoulders to learn the rules of the game you play.  If you win a game because your opponent didn't take the intiative to learn all the rules of play, it's substantially no different than if you won a game because your opponent was to lazy to do some simple calculations.

I don't find the rule all that complicated either. Yet there seems to be a mystical, confusing quality about en passant . I agree that it is your own responsibility to learn all the rules when playing chess or anything else.